Container losses from a stack collapse on an Ocean Network Express (ONE) boxship in the Atlantic earlier this month appear to be worse than first feared.

The Singapore-based liner operator said that in total it now estimates 60 containers went overboard, and 80 were damaged on the 13,900-teu Madrid Bridge (built 2018) in the 7 January incident.

Original estimates suggested only about 30 boxes may have been lost.

The full extent of the losses is unlikely to be known until the Madrid Bridge arrives at the US east coast in the next week.

The container ship has been diverted from its original destination New York, and will instead call at Charleston for a detailed assessment of the damage to the ship.

Containers affected by the incident will also be discharged.

The vessel was on ONE's East Coast 4 service when the incident happened as it sailed west from Europe.

AIS indicates the vessel sailed south of its original course after the incident, suggesting it was trying to avoid heavy weather.

Safety first

The ship is likely to be significantly delayed, but ONE said it is prioritising the safety of the crew and vessel.

"Our immediate priorities are to ensure the safety of the crew, the vessel and the cargo on board," the company said.

The incident has raised concern because there were a series of similar major container stack collapse incidents last winter in the Pacific.

The Madrid Bridge is owned by K Line, one of three Japanese shipping giants that are shareholders of ONE. Its protection and indemnity cover is with the Japan P&I Club.